I'm not sure if I would call it old fashioned, but PDF isn't interactive whereas our help section allows you to search and crosslink to other help topics, so we think that it is an improvement. You can always print the help pages out or save them to a PDF if you prefer the linear format.

... but PDF isn't interactive whereas our help section allows you to search and crosslink to other help topics...

While I agree with your conclusion that you will keep your help as is, PDFs are certainly easily searched via Find; and if the creator uses Acrobat Pro (or similar authoring prog) it is easy to:
create bookmarks - to help with organization and navigation for reader
make links - to other pages within PDF; to URLs; to pages within other PDFs.
As author you can also put sticky type notes (that can be collapsed or opened) with different colors to comment on an area of text.
As author (and as reader if you are using Pro) you can use highlighter in different colors - well to highlight.

PDFs have enormous advantages and I create them frequently for the internal training manuals I do for our small company. I want all of you to enhance TD, and am a bit amused at the lack of knowledge about PDFs, but I "pay you" to be experts in TD.

Coach.mac A suggestion for learning TD: Create a word doc dedicated to TD. Cut and paste parts of official help topics to it. Cut and paste forum posts or parts of them that have good suggestions for using TD to the word doc. In this way you are creating your own personalized user manual. I also keep in such a doc notes on when I started using a piece of software; my login and pw; my own hot keys and ways of using the software; etc.